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COI Seminar Series

Thursday, May 21, 2009

Redfield Auditorium - 12:00 Noon
Co-Sponsored by Biology Department

The Impact of Climate Change on Phenology, Productivity, and Benthic-Pelagic Coupling in Narragansett Bay

Scott Nixon
Graduate School of Oceanography
University of Rhode Island
Robinson (Wally) Fulweiler
Department of Earth Sciences
Boston University

The timing and magnitude of phytoplankton blooms have changed markedly in Narragansett Bay, RI (USA) over the last half century. The traditional winter-spring bloom has decreased or disappeared and shorter, often intense, summer diatom blooms have become common at other times, replacing the traditional flagellate blooms of the past. The mean abundance and biomass of phytoplankton appear to have decreased based on almost 50 years of biweekly monitoring by others at a mid bay station. These changes in phenology and the oligotrophication of Narragansett Bay appear to have greatly decreased the quantity and (perhaps) quality of the organic matter being deposited on the bottom. Benthic metabolism as reflected in oxygen uptake, nutrient regeneration, and the net flux of N2 gas has declined. During at least one summer, net denitrification was replaced by net heterotrophic N fixation. Higher trophic levels also appear to be affected as decades of standard weekly trawls show that the winter biomass of bottom feeding epibenthic animals has declined sharply at the mid bay station.